Composition consisting of novolac resins and aromatic polycarboxylic compounds

ABSTRACT

THERMOSETTABLE POLYMERIC COMPOSITIONS INCORPORATING A NOVOLAC RESIN AND AN AROMATIC POLYCARBOXYLIC COMPOUND. WHEN THERMOSET BY HEAT, THESE COMPOSITIONS DISPLAY IMPROVED THERMAL STABILITY.

United States Patent Olfice 3,558,560 Patented Jan. 26, 1971 Int. Cl. C08g 5/18 US. Cl. 260-59 6 Claims ABSTRACT OF THE DISCLOSURE Thermosettable polymeric compositions incorporating a novolac resin and an aromatic polycarboxylic compound. When thermoset by heat, these compositions display improved thermal stability.

BACKGROUND Heretofore, those skilled in the art of phenolic resins have long appreciated that such resins, especially those of the novolac type, have their thermosetting character enhanced or promoted through the use of curing agents, such as hexamethylenetetramine, and the like. The art has long sought to improve the characteristics of cured (crosslinked) thermosettable phenolic resins through varying either or both the chemical compositions and amounts, respectively, of phenolic resin and curing agent employed in any given instance.

One of the characteristics of thermoset phenolic resins which has been particularly difiicult to improve has been that of thermal stability, such as the ability of a particular thermoset phenolic resin to withstand, and be stable to, prolonged exposure to elevated temperature. Such thermal stability can be measured by any convenient means, such as by thermal gravimetric analysis, or by strength retention measurements (or weight loss measurements) of standardized laminate constructions (containing a given thermoset phenolic resin to be tested).

Such diificulties in improving thermal stability, recent evaluations have apparently shown, are probably inherently caused by the structural limitations in three-dimensional crosslinked phenolic resins. A cured phenolic resin does not heat soften or change dimensions upon heat exposure but instead tends to degrade and lose structural integrity once an inherent threshold temperature (typically, about 450 F.) has been exceeded for an appreciable period of time.

A new and much improved class of thermosettable phenolic resins has now been discovered. This class comprises a thermosettable mixture of novolac resins and aromatic polycarboxylic compounds. When compared with conventional novolacs conventionally cured (as with hexamethylenetetramine), this new class of phenolic resins has surprising thermal stability when thermoset. This improvement in thermal stability is, it is theorized (and there is no intent to be bound by theory herein), a result of the increased structural strength on a molecular crosslinking basis associated with these new phenolic resins.

SUMMARY prise at least one novolac phenolic resin and at least one aromatic polycarboxylic compound. Such a novolac resin is generally characterized by having:

(1) A number average molecular weight of from about 200 to 1000,

(2) At least two aryl moieties per molecule, the aryl nucleus of each aryl moiety containing from 6 through 10 carbon atoms each,

(3) At least one divalent bridging moiety of the formula:

wherein R and R are each individually selected from the group consisting of hydrogen, lower alkyl, lower alkalene, lower haloalkyl, aryl of from 6 through 12 carbon atoms, haloaryl of 6 through 12 carbon atoms, and heterocyclic structures containing rings with 5 or 6 members each, each individual ring containing an oxygen, a sulphur, or a nitrogen atom, each such heterocyclic structure being bonded to the carbon atom of said bridging moiety, said bridging moiety having the unsatisfied valences of its carbon atom each bonded to a different one of said aryl moieties,

(4) At least two OH groups per molecule, each such group being directly attached to a different one of said two aryl nuclei, and

(5) A percent oxygen acetyl of from about 10 to 30.

Similarly, such an aromatic polycarboxylic compound is characterized as being within the given class of compounds having the general formula:

in which R, is an aromatic radical of three, four, five or six valences and containing from 6 to 24 carbon atoms; R; is a monovalent hydrocarbon radical containing less than 19 carbon atoms; n is an integer of from 0 through 3; m is an integer of from 0 through 6; p is an integer of from 0 through 6; when n is O, the sum of m-l-p is an integer of from 3 through 6; when rr is 1, the sum of mH-p is an integer of from 1 through 4; when n is 2, the sum of m +p is an integer of from 0 through 2; and the sum of n and p is always at least 1.

Preferably R and R are both hydrogen, R contains a single six membered aromatic ring (i.e. phenyl), and R is a lower alkyl radical. The term lower as used herein refers to a radical containing less than seven carbon atoms.

In general, in any given composition of this invention, there is present for a given amount of such novolac resin, at least suflicient amount of such aromatic polycarboxylic compound to make the resulting composition thermosettable by heat alone (especially when such composition is in the form of a uniform mixture of the respective two components); for example, at a temperature of about 150 C.

In general, thermosetting of a thermosettable resin composition of this invention results from the reaction of an aromatic polycarboxylic compound with the reactable aromatic hydroxyl group in the novolac starting material. Sometimes as little as about 5 or 10 weight percent (or even less) of the stoichiometric amount (that is, the amount of dicarboxyl compound) needed to completely react on a 1:1 mol basis each reactable aromatic hydroxyl group with dicarboxyl compound. is suflicient to effect thermosetting. 0n the other hand, sometimes as much as percent excess (or even more) of the stoichiometric II o amount as just described of dicarboxyl compound is desirable in a composition of the invention to produce thermosetting of a composition of this invention. Preferably, from about 80 to 110 weight percent of such stoichiometric amount is employed.

For purposes of this invention, the term thermoset or thermosetting in reference to compositions of this invention indicates that a given thermosettable composition of this invention, after exposure to elevated temperatures for times sufiicient to substantially completely react together substantially all of one of the two components (depending upon which one is present in excess of stoichiometric amount) with the other component comprising a composition of this invention so as to produce a product which is not only substantially insoluble, but also is substantially infusible. For purposes of this invention, the term substantially insoluble in relation to thermoset or thermosetting has reference to insolubility in common organic solvents, such as methyl ethyl ketone, so that not more than about 10 weight percent of a given so thermoset product dissolves in such a solvent. Similarly, the term substantially infusible has reference to the fact that a given or thermoset product does not appreciably melt before decomposing when heated to elevated temperatures.

Because of the tendency for undesirable side reactions to occur (such as hydrolysis of the Formula 2 com pounds), and because of the possibility that the thermosettable compositions of this invention will not uniformly cross-link in the presence of appreciable amounts of moisture, the thermosettable compositions of this invention are prepared using novolacs and aromatic polycarboxylic compounds, respectively, in substantially anhydrous form. The term substantially anhydrous has reference to the fact that a given material contains initially less than about 5 weight percent free water (based on total weight) and preferably less than about 1 weight percent thereof and most preferably less than about /2 weight percent thereof.

THE NOVOLAC STARTING MATERIAL In general, any novolac resin known to the prior art having the above-described characteristics can be used in the compositions of this invention. Because of possible ambiguities in prior art teachings relating to production of novolacs, a brief discussion of the preparation and properties thereof is now given.

For purposes of this invention, total acetyl percent of novolac is conveniently determined by the method of Siggia.

Typical beginning materials suitable for use in making novolac resins are:

(A) A phenol which has at least one unsubstituted reactive position on the aromatic nucleus, and

(B) An aldehyde containing at least one aldehyde group.

The phenols which can be employed in this invention are aromatic alcohols which have at least one hydroxyl group directly attached to the aromatic nucleus and which have at least one unsubstituted reactive position on the aromatic nucleus. It is normally the case that the reactive positions on the aromatic nucleus are those which are ortho and para to the hydroxyl group. Therefore, phenols which have at least one unsubstituted position ortho or para to the hydroxyl group are particularly useful. Examples of representative and illustrative phenols which can be employed in this invention are given in Table I below:

TABLE I Examples of Phenols (1)11 lOH 4 TABLE I.Continued on (])H @0 can @-or TABLE I.--Continued (I)H Q- Q Preferred phenols are phenol itself, alkylphenols, and aryl phenols wherein substituents on this phenol benzene ring have a total of from 1 to 18 carbon atoms, and most preferably, from 1 to 6 carbon atoms.

The aldehydcs which can be employed are alkanals such as formaldehyde, aeetaldehyde, propionaldehyde and the like, arylals such as 'benzaldehyde, salicylaldehyde, and the like, haloalkanols, such as chloral, and the like. Formaldehyde is preferred. The formaldehyde can be employed in water solution or dispersion, or in an organic solvent such as methanol. It is preferred to employ the formaldehyde in aqueous solution (such as the 37 weight percent aqueous solution known as formalin). Paraform can also be used.

Suitable aromatic phenol-aldehyde compounds which can be used in the manufacture of novolac starting materials (usually not more than about 10 weight percent of total reactants, based on phenol) are shown in Table 11 below.

TABLE H Examples of Aromatic Phenol-Aldehyde Compounds OH OH @TGHO CHO OH OH 0110 CHO I CHO OH OH CHO OLE[O When one makes a novolac resin using, for example, a phenol, and an aldehyde, it is convenient and preferred to condense the starting materials under aqueous liquid phase conditions using heat and acid catalyst. Conventional and preferred acid catalysts are inorganic mineral acids, such as sulfuric acid and organic carboxylic acids (mono or polybasic) which are relatively strong as respects their disassociation constants. Examples of suitable such acid catalysts include: aliphatic carboxylic acids, such as formic, propionic, oxalic, diglycolic, fumaric, itaconic, lactic, maleic, malonic, and the like, and aromatic mono and dicanboxylic acids, such as naphthoic, phthalic, salicyclic, and the like.

The amount of acid catalyst employed can vary but in general is sufficient to produce a pH in an aqueous liquid phase medium of from about 0.5 to 4.0 (preferably from about 1.0 to 3.0) but this is not necessarily a critical factor. For such a condensation, the acid catalyst is preferably formic acid, oxalic acid, or propionic acid in an amount of from about 0.5 to 5 parts catalyst per parts phenol (by weight). The temperature of reactants in such preferred embodiment can vary from about 60 to 100 C. Agitation of reactions during condensation is preferably continuous. It is not necesary for the reactants to be charged together to a reactor; thus, formaldehyde can be slowly added to a warmed mixture of aniline, phenol and acid catalyst. The entire condensation may be carried out at reflux temperatures if desired. Since a cocondensation reaction is apparently involved, the reaction mechanism, it is theorized, may involve formation of low molecular weight intermediates which initially form, and then possibly rearrange and combine with one another at a later stage. Typically, condensation reaction conditions are maintained until all aldehyde is consumed.

In general, conventional equipment can be employed for the condensation reaction. For example, a reaction kettle equipped with agitator, means for reflux and distillation, nitrogen inlet means, and conventional heat transfer means is suitable. The material of construction can be steel, stainless steel, glass, Monel, or the like.

In general, a preferred method for carrying out the condensation reaction of the phenol, aldehyde, is to add the aldehyde slowly to an agitated. mixture of phenol and aromatic amine containing the acid catalyst. This mixture is maintained at a temperature of from about 50 C. to about 125 C., and preferably from about 70 C. to about C. during the addition. After the addition of aldehyde, which can take from about one hour to about four hours or longer, the condensation reaction is continued for about 30 minutes to about 3 hours at a reaction temperature of from about 50 C. to about 125 C., and preferably from about 95 C. to about 100 C. At the end of the reaction period, the condensation product can then be recovered by stripping off Water and unreacted reagents under reduced pressure at temperatures from about C. to about 200 C., and preferably, from about 140 C. to about 170 C.

Another method for carrying out the condensation reaction is to methylolate a phenol (monomethylolation) by reacting a phenol with an aldehyde under base catalysis at temperatures of from about 50 C. to about 110 C., and preferably from about 60 C. to about 80 C. The reaction mixture is then made (slightly) acidic (if not already so) and additional phenol is added and condensed with the foregoing at temperature of froma bout 50 C. to about C., and preferably, from about 95 C. to about 100 C. At the end of the reaction period, the condensation product can be recovered by stripping olf water and unreacted reagents under reduced pressure at temperatures from about 110 C. to about 200 C. and preferably, from about C. to about C. Yet another method for carrying out the condensation reaction is to make a phenolic novolac resin using the well known acid catalyzed reaction of phenol and aldehyde. The unrecovered phenolic resin (containing water and unreacted phenol) is then made mildly acidic (if not already so) and the additional phenol added. The final condensation is then carried out by adding further aldehyde to the foregoing mixture while being maintained at a temperature of from about 50 C. to about 125 C., and pref- 8 THE AROMATIC POLYCARBOXYLIC COMPOUNDS Turning to the aromatic polycarboxylic compounds of Formula 2, it will be appreciated that R the monovalent hydrocarbon radical, is not a critical function in the resent invention and ma be an monovalent alkl erably fr.om abgmt 95 to about 4 At the end of arylf or even a cycloalkyl, hal genoallzyl, halogenoaryl Y); the reacnon f q the condensatlon product can be other halo-substituted radical (preferred chloro). The Covered by Stnppmg off Water and unreacted reagentsoun' preferred monovalent hydrocarbon radicals are alkyl def reduced pct-assure at temperatures from about radicals, especially those containing from 1 through to about 2 and preferably from about 140 10 carbon atoms. The aromatic carbonyl-containing comto about 170 pound must contain at least two carbonyl-containing In gener as first Prepared the novolac 1S typlcany an groups in the ortho position. The anhydride groups each aqueous solution or dispersion, the exact conditions and with a valence of two and each containing two caronyL respective quantities and types of reactions in any given containing groups always attached to adjacent instance being determinative of the character of the prodbon atoms on aromatic ring The Formula 2 net (including degree of advancement, color, etc.). The pounds can contain any combination of anhydn-de acid phenolic resin can be concentrated (and even prepared or ester groups, as defined in Formula A preferre as a solid resin) and impurities such as unreacted reacnumber f carbony1 containing groups per molecule is tants largely removed by means of dehydration under four Such as two anhydride groups, f ester groups, Vacllllm- AS those Skilled in the art Pp yp or a combination of any four of these carbonyl-containing hydration conditions are distillation under about 28 inches groups A ti l l preferred aromatic b l mercury vacuum until batch temperature reaches about taining compound is trimellitic acid anhydride. The aro- 160 C. though any convenient conditions can be emmatic radicals must each contain at least two carbonylployed. containing groups attached to adjacent carbon atoms Yields of novolac resin typically vary from about 85 Whereas the other Carbonyl-Containing groups can be 011 to 110 percent (based on combined starting (charged) y other ring Positionweights of aromatic amine and phenol) As a class, the compounds or: Formula 2 are known, as In general, for use in the present invention, novolac 3i: Egg?li if t gz i fgggg (so detalls concemmg resins are prepared in the form of substantially anhydrous starting materials, as explained above. 30 F represengatwi i lllilstrzatlve l i An advantage in dehydrating a starting novolac is that .ggg iz fi g s ggf ig S 0 0mm a are glven m the dehydration procedure (using heat and reduced pressure as described above) typically also tends to remove TABLE III impurities from a starting resin, such as unreacted starting materials, catalysts, etc. Examples of Formula (2) Anhydride Compounds O\ /O O O 0 0 O O c 0 C 2 O f 0 0 Q '15 TABLE IV Examples of Formula (2) Esters and Half Ester m C m w o CH0 m 0H0 M H D n-U o P 4 0 m w m H m m J 4 J 0H0 JUNO o nu CI IO w o H w H O C O C H044 EQW O O TABLE IV.-Continued In general, for use in the present invention, aromatic polycarboxylic compounds are prepared in the form of substantially anhydrous starting materials, as explained above.

PREPARATION OF COMPOSITIONS To make a thermosettable resinous composition of this invention, one takes a novolac resin as described above and an aromatic polycarboxylic compound as de scribed above and simply mixes the two components together until a substantially uniform product mixture is obtained. The relative proportions of each are as described above.

In general, the proportion of aromatic polycarboxylic compound to novolac resin in any given thermosettable composition is such that the composition will thermoset when exposed to an elevated temperature, e.g., a temperature of 180 C. or higher. Preferably, the proportion of aromatic polycarboxylic compound to novolac resin is such that ester linkages can be formed at each phenolic hydroxyl site within each novolac resin molecule. However, thermosettability is frequently achievable by using less than all such phenolic hydroxyl sites when crosslinking with an aromatic polycarboxylic compound such as taught in this invention. Also, thermosettability is not appreciably alfected, within wide limits, by using excesses of stoichiometric amounts of aromatic polycarboxylic compounds in relation to a given quantity of another modified novolac resin. Rate of ester formation can be promoted by use of catalysts such as p-toluene sulfonic acids, boron trifiuoride and alkyl titanates.

In general, the thermosettable resinous compositions of this invention, owing to the initial substantially dehydrated character of each of the novolac resin and of the aromatic polycarboxylic compounds, respectively, employed in these compositions, are in the form of either powders which are characteristically free flowing, or liquids which are in the form of solutions or dispersions with the liquid medium thereof being organic and substantially anhydrous in character.

When making a solid, thermosettable composition of this invention, it is preferred to use a novolac resin and an aromatic polycarboxylic compound (as described above, respectively) in the form of solids which have particle sizes generally under about mesh (US. Standard sieves). Preferably, particle sizes under about 50 mesh are used. The admixing of one component with the other can be made in a blender, such as a so-called Waring Blendor, a ball mill, or the like, although any convenient mechanical mixing means may be employed.

On the other hand, when preparing a liquid thermosettable composition of this invention, either or both the novolac or the aromatic polycarboxylic compound may intially be in a solid or a liquid form. Thus, the novolac resin even in its substantially anhydrous form may be in a liquid condition. Although the aromatic polycarboxylic compound even in its dehydrated form may also be in a liquid condition, typically such aromatic polycarboxylic compound is in the form of a high melting solid.

As indicated, an organic liquid is used to dissolve or disperse either or both the novolac resin and the aromatic polycarboxylic compound. In general, the organic liquid used is one which is:

(l) Substantially inert (as respects each of the novolac resin and the aromatic polycarboxylic compound),

(2) Boils below about 250 C. (preferably 150 C.) at atmospheric pressures,

(3) Is a mutual dispersant for both the novolac resin and the aromatic polycarboxylic compound, and

(4) Is substantially single phased.

By the term mutual dispersan as used herein reference is had to the fact that a given organic liquid is capable of acting either as a solvent and/ or as a colloidal suspending medium for the novolac resin and for the aromatic polycarboxylic compound in a product thermosettable composition of this invention. As used herein, the term colloidal in reference to a suspension or dispersion'has reference to suspended or dispersed solid particles which are under about 200 millimicrons in average maximum individual particle size dimension.

By the term substantially single phased reference is bad to the fact that a given organic liquid exists in a liquid composition of this invention as one phase.

While the organic liquid used has properties as indicated above, it will be appreciated that such a liquid in a particular composition of the invention can comprise mixtures of two or more chemically different organic liquids. For example, one can preliminarily dissolve or disperse the novolac resin in one particular liquid, and the aromatic polycarboxylic compound in another particular organic liquid, and then thereafter mix the two resulting such organic liquids together. Obviously, when one uses such a mixture of different organic liquids, the liquids are so chosen as to be mutually inter-miscible with one another at least in the respective amounts of the individual organic liquids employed in a given product mixture in order to obtain a compatible one-phase liquid medium.

It is desirable and preferred to have a single phase organic liquid in liquid thermosettable compositions of this invention because of the possibility of having a concentration either of aromatic polycarboxylic compound or of novolac resin which is greater in one liquid phase than in the other. Such a concentration differential could possibly lead to irregularities and nonuniformities in a thermoset composition derived therefrom, as those skilled in the art will appreciate.

Preferred organic liquids (especially when one is using) as the organic liquid a single chemical entity, are lower alkanones, such as acetone, methyl ethyl ketone or higher ketone. On the other hand, when one uses as the organic liquid a mixture of dilferent organic entities, one can employ as preferred liquids lower alkanols (such as ethanol or methanol, aromatic and aliphatic) (including cycloaliphatic hydrocarbons), including benzene, toluene, xylene, naphthalene, nonane, octane, petroleum fractions, etc. Conveniently, some of the organic liquid present can be excess alcohol left over from an esterification reaction involving an aromatic polycarboxylic compound. Any given organic liquid used in a composition of this invention is substantially anhydrous, as indicated above.

Preferably, the novolac resin starting materials are substantially completely dissolved in the organic liquid phase of a liquid composition of this invention. If not so dissolved, the nondissolved portion thereof is in the form of a colloidal dispersion or suspension of particles. Preferably, at least 80 percent of the novolac resin is completely dissolved in the organic liquid and more preferably such resin is substantially completely dissolved in the organic liquid.

Similarly, the aromatic polycarboxylic compound starting materials are substantially completely dissolved in the organic liquid phase of a liquid composition of this invention. If not so dissolved, the nondissolved portion thereof is in the form of a colloidal dispersion or suspension of particles. Preferably, at least 80 percent of the aromatic polycarboxylic compound is completely dissolved in the organic liquid and more preferably such resin is substantially completely dissolved in the organic liquid.

Those skilled in the art will appreciate that organic solvents can be added to a given liquid composition of this invention to improve the quantity of respective starting materials in true solution. For example, adding a ketone or an ester ether solvent, or even a so-called super solvent, such as dimethyl formamide, will generally improve the ability of a given composition to dissolve both classes of component starting materials. If dimethyl formamide is employed, it is preferred to use not more than about 20 weight percent of this material based on total organic liquid weight in a given liquid composition.

The respective concentrations of the novolac resin and of the aromatic polycarboxylic compound in a given liquid composition of this invention relative to the total amount of organic liquid present can vary over extremely wide ranges. A rough but practical indication of the concentration of the respective starting materials in a given liquid composition is given by the viscosity of such a composition. A correlation between viscosity and particular contemplated end use can sometimes be made, as those skilled in the art will readily appreciate. Characteristically, though not limitatively, a liquid composition of this invention can have viscosities: ranging from about 10 to 5000 centipoises. For impregnating applications, viscosities of from about 50-500 centipoises are usually preferred. The total solids content of a given liquid composition can be as high as about 75 weight percent or even higher, and as low as about 20 weight percent or even lower. Preferred solids contents usually fall in the range of from about 50 to 70 weight percent as those skilled in the art will readily appreciate.

Liquid compositions of this invention can be advanced (e.g., cross-linked as by heating) to some extent without forming precipitates from the organic liquid. Advancing can be accomplished if desired by heating at temperatures generally in the range of from about 70 to at atmospheric pressures for times typically in the range of from about 20 to 30 minutes or even longer, care being taken not to cause solid material to precipitate.

In both the solid and the liquid compositions of this invention, it will be appreciated that the ratio of novolac resin to aromatic polycarboxylic compounds is as indicated above. However, mixtures of different novolac resins and of different aromatic polycarboxylic compounds can be employed in any given composition to enhance characteristics desired for a particular end use application as those skilled in the art will readily appreciate.

Those skilled in the art will readily appreciate that various conventional additives can be composited with the solid or liquid compositions of this invention to promote effectiveness for particular end uses. For example, one can add dyes, colorants, release agents, fungicides, coupling agents, and the like.

In the case of the powdered products of this invention, one can add particulate solid diluent materials to produce molding compositions. For example, a typical molding composition using a composition of this invention contains from about 25 to 40 weight percent of a composition of this invention, and, correspondingly, from about 60 to 75 weight percent of particulate inert diluent. A molding composition typically contains in addition from about 1 to 2 weight percent of a lubricant and from about 1 to 2 weight percent of a colorant, though relatively higher percentages of these last indicated components can be present herein.

USES

As indicated above, the solid compositions of this invention can be used as molding powders. In general, conventional molding powder technology can be employed in the utilization of such solid compositions. Sometimes it is desirable in order to avoid blistering to cool a given mold as those skilled in the art will appreciate. The solid resins can also be used to bond aluminum oxide grits commercially utilized in abrasives.

The liquid compositions of this invention find use for impregnation and reinforcing purposes. Thus, the liquid compositions can be used to impregnate cellulosic paper, asbestos paper and other known woven sheet structures as well as woven fabrics (such as glass fibers, cotton fibers, nylon fibers, etc.) and the like. impregnation can be accomplished by any conventional or convenient means including dipping, coating, spraying, or the like. The so-impregnated material is conventionally air-dried to lower the volatiles content and then is heated to advance the composition of this invention to a particular desired degree for the ultimate intended use. The so-impregnated sheet materials are themselves particularly useful in the manufacture of laminates. Such laminates, such as those 24 ously. The temperature of the reaction mixture increased until refluxing started after which the temperature gradually dropped to about 101 C. by the end of the formaldehyde addition. The reaction mixture is then refluxed for about 4 hours at about 100 C. The reaction flask is then changed over to vacuum distillation conditions and vacuum slowly applied up to about 7" Hg (temperature leveled at about 90 Q). As the temperature reached about 95 C. (with about 7" Hg vacuum), the vacuum is increased slowly to about 10 Hg. When the temperature reached about 100 C., the vacuum is increased slowly to about 20" Hg. As the temperature reached about 110 C., the vacuum is increased slowly to 28" Hg. The temperature is then allowed to rise to 160 C. with made from impregnated sheet materials as indicated above 28 Hg of vacuum while continuing to distill. At 160 are useful in electrical applications as supports or as C., the distillation is stopped and the product poured insulation for conductive elements. The laminates so made into a pan to cool. The resulting phenol-formaldehyde are particularly characterized by superior heat resistance novolac is a clear, brittle, glasslike solid at room temand thermal stability characteristics. The laminates are perature. The yield of solid resin is about 100 percent generally manufactured in a sheet or block form which is based on the phenol charge.

then machined to provide desired configuration for a par- Exa m pl 6 B ticular end use.

Oil filters, such as for use in automobiles, can be pre- Following the same general procedure described in pared from the impregnated sheet members produced as Example A, a series of phenol-aldehyde novolac resins generally described above. For example, one can impregare prepared from various phenols and aldehydesz:

TABLE 1 Example B o D E F Phenol Phenol p-Cresol p-t-Butyl phenoL. Phenol p-Chlorophenol. Aldehyde For aldehyde Formaldehyde Formaldehyde.. Acetaldehyde... Formaldehyde. Molar ratio of aldehyde to phenol 0.85/1 0.75 l 0.80 l 0.80 0.75 1. Catalyst Oxalic acid Formic acid Oxalie acid Oxalic acid Formic acid.

nate with a liquid composition of this invention, cellulosic papers modified with a synthetic fiber such as a polyester or the like and having a thickness of from about 5 to 20 mils. Suflicient liquid composition is used to impregnate such a sheet member so that the product sheet member when cured has a resin content of from about 15 to 25 weight percent based on the total product weight. After such a paper is impregnated, it is typically heated to partially advance the resin composition, and then is corrugated or pleated to form a filter element. The filter element is then assembled with an end use filter condenser and the whole assembly is heated to say from about 250 to 350 F. for from about 5 to 20 minutes to cure the resin. When cured, the product has excellent high temperature characteristics.

In addition, a liquid composition of the present invention can be used to make reinforced plastics.

In this invention, all solids in liquids are conveniently measured using ASTM Test Procedure D115-55.

EMBODIMENTS The following examples are set forth to illustrate more clearly the principles and practices of this invention to one skilled in the art and they are not intended to be restrictive but merely to be illustrative of the invention herein contained. Unless otherwise stated therein, all parts and percentages are on a weight basis.

The following examples illustrate preparation of novolac resins.

PREPARATION OF PHENOL-ALDEHYDE NOVOLAC RESINS Example A 2820 grams moles) of phenol is heated to 95 C. in a 5-liter, 3-neck Pyrex reaction flask that is equipped with stirring thermometer, reflux condenser and dropping funnel. At 95 C., 113 grams (2.73 moles) of 90 percent strength formic acid is added and allowed to mix. Next, over about a 1 /2 hour period, 1438 grams (24 moles) of 50 Weight percent aqueous formaldehyde solution is added to the reaction mixture while stirring vigor- Example G Preparation of /2 dibutyl ester of benzophenone tetracarboxylic acid dianhydride solution A mixture of 1500 grams (20.3 moles) of n-butyl alcohol and 1250 grams (3.88 moles) of tetracarboxylic acid dianhydride (BTDA) is heated over a period of about one hour to about 125 C. in a 5-liter, 3-neck Pyrex reaction flask that is equipped with stirrer, thermometer and reflux condenser. At about 123 C., the foregoing mixture becomes clear. It is then allowed to cool slowly to room temperature at which temperature it remained a clear, amber colored liquid of medium viscosity. Yield: about 2750 grams.

Example H Preparation of /2 butyl ester of trimellitic anhydride Preparation of mixed /2 dipropyl ester of benzophenone tetracarboxylic acid dianhydride and trimellitic anhydride solution A mixture of 2000 grams (33.3 moles) of n-propyl alcohol, 1000 grams (3.11 moles) of benzophenone tetracarboxylic acid dianhydride (BTDA) and 1000 grams (5.21 moles) of trimellitic anhydride (TMA) is heated over a period of about one hour to about C. in a 5-liter, 3-neck Pyrex reaction flask that is equipped with stirrer, thermometer and reflux condenser, At about 102 C., the foregoing mixture becomes clear. Upon allowing it to cool slowly, it starts to become cloudy at about 75 C. and is a white colored liquid dispersion of medium viscosity at room temperature. Yield: about 4000 grams.

Example I Preparation of solid /2 butyl ester of benzophenone tetracarboxylic acid dianhydride 26 EXAMPLE 7 Preparation of thermosetting resin powder from phenolic novolac resin and an aromatic polycarboxylic compound 500 grams of resin from 'Example A, 500 grams of aromatic polycarboxylic compound from Example 1 and 10 grams of calcium stearate are ground together in a laboratory ball mill until essentially all of the material passes U.S. sieve No. 140. The product is a tan colored resin powder. When a small amount (1-2 grams) is placed on a hot plate at about 180 C., this resin melts and then cures to a hard, thermoset resin.

EXAMPLES 8-10 Following the same general procedure described in Example 7, a series of resin powders are prepared from phenolic novolac resins and aromatic polycarboxylic compounds. Table 3 below describes each resin.

TABLE 2 Resin identification (Ex. No.) B B B C F Part A. Solvent MEK MEK MEK Cellosolve MEK Resin concentration 50% 50% 50% 60% 60% Aromatic polycarboxylic com- G H K I G pound identification (Ex. Part B. No.).

Ratio by weight 01A to B in 1.3/1 1.7/1 1.1/1 1.5/1 1.4/1

final varnish.

condensation product is a clear, brittle, glasslike solid at TABLE 3 room temperature which shows a tendency to become sticky in the presence of moisture. Yield: about 1425 8 9 10 grams, PART A Rcsinidentification (Ex. No.) B I) E 1 Aromalziic pglycagborylic e&m J J J xam poun i en lea ion x. E pe K PART B 0.

Ratio by weight of A to B in 1/1 2/1 1/1 Preparation of tetrahexyl ester of pyrornellitic dianhydride A mixture of 2448 grams (24 moles) of n-hexyl alcohol, 655 grams (3 moles) of pyromellitic dianhydride (PMDA) and 15 grams (0.08 mole) of p-toluene sulfonic acid is refluxed at about 160 C. for 8 hours in a 5-liter, 3-neck Pyrex reaction flask that is equipped with stirrer, thermometer and reflux condenser. The water formed is removed by distillation. The product is a liquid of low viscosity.

Examples of compositions of this invention follow.

EXAMPLE 1 Preparation of thermosetting varnish from phenolic novolac resin and an aromatic polycarboxylic compound A 50 percent resin solution is made by dissolving 1000 grams of the solid resin from Example A in 1000 grams of Cellosolve. Alternatively, this solution is made by adding the solvent to the molten resin at the end of the resin distillation cycle. The resulting solution is a clear, amber, colored liquid of medium viscosity. To this solution is added 1470 grams of /2 dibutyl ester of hemephenone tetracarboxylic acid dianhydride solution from Example G. In addition, an esterification catalyst such as tetrabutyl titanate may be added. With suflicient mechanical blending, the mixture gave a clear, amber colored varnish. When a small amount (1-2 grams) is placed on a hot plate at about 180 C., this varnish cures to a hard thermoset resin. Properties of this varnish are as follows: Viscosity about 500 cps. and ASTM solids about 65 percent.

EXAMPLES 2-6 Following the same procedure described in Example 1, a series of varnishes are prepared from phenolic novolac resins and aromatic polycarboxylic compounds. Table 2 below describes each resin.

final product.

What is claimed is: 1. A thermosettable resinous composition consisting of: (A) a novolac resin characterized by having:

(1) a number average molecular weight of from about 200 to 1000, (2) at least two aryl moieties per molecule, the aryl nucleus of each aryl moiety containing from 6 through 10 carbon atoms each, (3) at least one divalent bridging moiety of the formula:

wherein R and R are each individually selected from the group consisting of hydrogen lower alkyl, lower alkalene, lower haloalkyl aryl of from 6 through 12 carbon atoms, and haloaryl of 6 through 12 carbon atoms, said bridging moiety having the unsatisfied valences of its carbon atom each bonded to a different one of said aryl moieties,

(4) at least one -OH group per molecule each such group being directly attached to a different one of said two aryl nuclei, and

(5) a percent oxygen acetyl of from about 10 to 30, and

(B) an aromatic polycarboxylic compound of the formula:

in which R is an aromatic radical of three, four, five, or six valences and containing from 6 to 24 carbon atoms, R, is a monovalent hydrocarbon radical containing less than 19 carbon atoms; 11 is an integer of from through 3; m is an integer of from 0 through 6; p is an integer of from 0 through 6; when n is 0, the sum of m+p is an integer of from 3 through 6; when n is 1, the sum of m+p is an integer of from 1 through 4; when n is 2, the sum of m+p is an integer of from 0 through 2; and the sum of n and p is always at least 1,

(C) the relative proportions of said novolac and said aromatic polycarboxylic compound being such that said composition is thermosettable by heat.

2. A thermoset composition of claim 1.

3. A composition of claim 1 wherein said compounds are suspended in an organic solvent medium.

4. A composition of claim 1 wherein said aromatic polycarboxylic compound is an ester of trimellitic anhydride.

5. A composition of claim 1 wherein said aromatic polycarboxylic compound is an ester of benzophenone tetracarboxylic anhydride.

6. A composition of claim 1 wherein said aromatic hydride.

References Cited UNITED STATES PATENTS 12/1912 Aylsworth 26059 7/1935 Carswell 26031.8 11/1959 Less et a1. 26031.8 12/1959 Kottler et al. 26018 3/1968 Bean et a1 26028 OTHER REFERENCES Ellis: Chemistry of Synthetic Resins, pp. 314-321, 414- 415 and 430431, 1935.

Chem. Abstracts, vol. 64, 1966, 8491 f-q, Hysol.

WILLIAM H. SHORT, Primary Examiner H. SCHAIN, Assistant Examiner US. Cl. X.R. 

